阅读说明：本技术 一种稀土掺杂二氧化硅气凝胶的制备方法 (Preparation method of rare earth doped silicon dioxide aerogel ) 是由 余煜玺 李璐 于 2021-09-17 设计创作，主要内容包括：一种稀土掺杂二氧化硅气凝胶的制备方法,属于气凝胶制备。将正硅酸乙酯、乙醇与水按比例依次加入容器中,机械搅拌后,加入盐酸再搅拌,密封静置充分水解反应后得SiO-(2)溶胶；将Y(NO-(3))-(3)·4H-(2)O粉末溶于水中,加热反应后冷却至室温后得到Y(NO-(3))-(3)溶液,滴入SiO-(2)溶胶中,搅匀；再滴入氨水,静置得Y-SiO-(2)凝胶；密闭静置老化后进行超临界干燥得块状Y-SiO-(2)气凝胶。通过在二氧化硅气凝胶中掺入稀土元素,提高二氧化硅气凝胶使用温度,降低气凝胶导热系数,所得气凝胶密度低、比表面积高,有良好隔热性能。方法工艺简单,生产效率高,设备要求较低,利于大规模生产,避免稀土元素在二氧化硅基体中分散不均匀的问题。(A preparation method of rare earth doped silicon dioxide aerogel belongs to aerogel preparation. Sequentially adding ethyl orthosilicate, ethanol and water into a container according to a certain proportion, mechanically stirring, adding hydrochloric acid, stirring again, sealing, standing, fully hydrolyzing to obtain SiO 2 Sol; mixing Y (NO) 3 ) 3 ·4H 2 Dissolving O powder in water, heating for reaction, and cooling to room temperature to obtain Y (NO) 3 ) 3 Dropping SiO into the solution 2 Stirring in the sol; then ammonia water is dropped in, and Y-SiO is obtained after standing 2 Gelling; carrying out supercritical drying after closed standing and aging to obtain blocky Y-SiO 2 An aerogel. By doping rare earth elements into the silicon dioxide aerogel, the use temperature of the silicon dioxide aerogel is improved, the heat conductivity coefficient of the aerogel is reduced, and the obtained aerogel is low in density, high in specific surface area and good in heat insulation performance. The method has simple process, high production efficiency, low equipment requirement, and is suitable for large-scale productionThe problem of uneven dispersion of the rare earth elements in the silicon dioxide matrix is solved.)

1. The preparation method of the rare earth doped silica aerogel is characterized by comprising the following steps of:

1) sequentially adding ethyl orthosilicate, ethanol and water into a container according to a certain proportion, mechanically stirring, adding hydrochloric acid, stirring again, sealing and standing at room temperature, and fully hydrolyzing to obtain SiO₂Sol;

2) mixing Y (NO)₃)₃·4H₂Dissolving O powder in water, heating for reaction, and cooling to room temperature to obtain Y (NO)₃)₃A solution;

3) mixing Y (NO)₃)₃Slowly dripping the solution into the SiO obtained in the step 1)₂Stirring uniformly in the sol;

4) adding ammonia water into the material obtained in the step 3), stirring uniformly, and standing to obtain Y-SiO₂Gelling;

5) mixing the above Y-SiO₂Carrying out supercritical drying after the gel is sealed, kept stand and aged to obtain blocky Y-SiO₂An aerogel.

2. The method for preparing rare earth-doped silica aerogel according to claim 1, wherein in the step 1), the molar ratio of the ethyl orthosilicate, the ethanol and the water is 1: (7-20): 3.

3. The method for preparing rare earth doped silica aerogel according to claim 1, wherein in the step 1), the mechanical stirring time is 10-15 min; the re-stirring time can be 100-120 min.

4. The method for preparing rare earth doped silica aerogel according to claim 1, which comprisesIs characterized in that in the step 1), the hydrochloric acid is added dropwise through a constant pressure funnel; the mass fraction of the hydrochloric acid is 0.05-0.1 wt%, and the molar ratio of the ethyl orthosilicate to the hydrochloric acid can be 1: 10^-4。

5. The method for preparing rare earth doped silica aerogel according to claim 1, wherein in the step 1), the sealing and standing time is 22-24 h, so that the hydrolysis reaction is sufficiently and slowly performed.

6. The method for preparing rare earth doped silica aerogel according to claim 1, wherein in the step 2), the temperature of the heating reaction is 45-50 ℃, and the time of the heating reaction is 30-35 min.

7. The method for preparing rare earth doped silica aerogel according to claim 1, wherein in step 2), Y (NO) is added₃)₃·4H₂The mass ratio of the O powder to the water can be 3-4: 1.

8. The method for preparing rare earth-doped silica aerogel according to claim 1, wherein in the step 4), the molar ratio of the tetraethoxysilane to the ammonia water in the material is 1: 0.1-0.25.

9. The method for preparing rare earth doped silica aerogel according to claim 1, wherein in the step 5), the standing and aging time is 22-24 h.

10. The method for preparing rare earth doped silica aerogel according to claim 1, wherein the supercritical drying conditions are as follows: ethanol is used as a supercritical drying medium, and N is pre-charged₂Heating the temperature in the kettle to 270 ℃ at the heating rate of 1 ℃/min until the pressure in the kettle is 2MPa, keeping the temperature for 2-4 h until the pressure in the kettle is 8-10 MPa, opening a water cooling device, slowly releasing the pressure in the kettle to normal pressure, and introducing N₂PurgingCooling to room temperature in the kettle to obtain Y-SiO₂An aerogel.

Technical Field

The invention belongs to the technical field of aerogel preparation, and particularly relates to a preparation method of rare earth doped silicon dioxide aerogel.

Background

Following a supersonic aircraftThe rapid development, the nose cone, the wings and the jet pipe of the engine of the aircraft are subjected to pneumatic heating for a long time, and the traditional heat-insulating material cannot meet the current use requirement, so that the development of the heat-insulating material with excellent comprehensive performance is very necessary. Aerogel is a novel heat insulation material with nano-scale holes, wherein SiO₂Aerogels are currently most widely used. But due to SiO₂Aerogel is easy to sinter at high temperature and has structural collapse, and the long-term use temperature of the aerogel is only 650 ℃. And thus its high temperature stability is generally enhanced by the incorporation of foreign elements. The rare earth silicate serving as an environment barrier coating has good high-temperature stability and excellent heat insulation performance, but the existing rare earth silicate ceramic has low porosity (50-70%) and large pore diameter (0.4-3.5 um), and the heat conductivity of the rare earth silicate ceramic rapidly rises in a high-temperature environment, so that the rare earth silicate ceramic is not suitable for high-temperature heat insulation. Because the rare earth element can form a novel material with different performances and various varieties with other materials, the rare earth doped silicon dioxide aerogel can have the excellent nano structure of the aerogel and the temperature resistance of the rare earth material, and has very great application prospect in the aspects of heat preservation and heat insulation.

Disclosure of Invention

The invention aims to provide a preparation method of rare earth doped silica aerogel, which can improve the use temperature of the silica aerogel, expand the application of the aerogel under high-temperature extreme conditions, and control the density and microstructure of the aerogel so as to control the heat conductivity coefficient of the aerogel, has simple and easy process and high production efficiency, and is beneficial to large-scale production.

The invention comprises the following steps:

1) sequentially adding ethyl orthosilicate, ethanol and water into a container according to a certain proportion, mechanically stirring, adding hydrochloric acid, stirring again, sealing and standing at room temperature, and fully hydrolyzing to obtain SiO₂Sol;

in the step 1), the molar ratio of the ethyl orthosilicate, the ethanol and the water is 1: 7-20: 3; the mechanical stirring time is 10-15 min; the hydrochloric acid can be added dropwise through a constant pressure funnel; the mass fraction of the hydrochloric acid is 0.05-0.1 wt%, and the ethyl orthosilicate isThe molar ratio of hydrochloric acid to hydrochloric acid may be 1: 10^-4(ii) a The re-stirring time can be 100-120 min; the sealing and standing time can be 22-24 h, so that the hydrolysis reaction is fully and slowly carried out.

2) Mixing Y (NO)₃)₃·4H₂Dissolving O powder in water, heating for reaction, and cooling to room temperature to obtain Y (NO)₃)₃A solution;

in the step 2), the temperature of the heating reaction can be 45-50 ℃, and the time of the heating reaction can be 30-35 min; the Y (NO)₃)₃·4H₂The mass ratio of the O powder to the water can be 3-4: 1.

3) Mixing Y (NO)₃)₃Slowly dripping the solution into the SiO obtained in the step 1)₂Stirring uniformly in the sol;

4) adding ammonia water into the material obtained in the step 3), stirring uniformly, and standing to obtain Y-SiO₂Gelling;

in the step 4), the molar ratio of the ethyl orthosilicate to the ammonia water in the material can be 1: 0.1-0.25.

5) Mixing the above Y-SiO₂Carrying out supercritical drying after the gel is sealed, kept stand and aged to obtain blocky Y-SiO₂An aerogel.

In the step 5), the standing and aging time can be 22-24 h; the supercritical drying conditions may be: ethanol is used as a supercritical drying medium, and N is pre-charged₂Heating the temperature in the kettle to 270 ℃ at the heating rate of 1 ℃/min until the pressure in the kettle is 2MPa, keeping the temperature for 2-4 h until the pressure in the kettle is 8-10 MPa, opening a water cooling device, slowly releasing the pressure in the kettle to normal pressure, and introducing N₂Blowing the mixture in a kettle, cooling the mixture to room temperature to obtain Y-SiO₂An aerogel.

According to the invention, tetraethoxysilane and rare earth nitrate are used as raw materials, ethanol is used as a solvent, acid and alkali are used as catalysts, a sol-gel method is adopted to prepare rare earth doped silica wet gel, and the bulk rare earth doped silica aerogel is obtained after ethanol supercritical drying. The prepared aerogel has low density, high specific surface area and good heat insulation performance. The preparation process of the aerogel is simple and easy to implement, high in production efficiency, low in equipment requirement and beneficial to large-scale production. The use temperature of the silicon dioxide aerogel can be increased, and the application of the aerogel under the high-temperature extreme condition is expanded. According to the invention, the density and microstructure of the aerogel can be controlled by controlling the ethanol content, the rare earth doping amount, the forming process and the like, so that the heat conductivity coefficient of the aerogel is controlled. Meanwhile, in the sol-gel process, liquid-phase heterogeneous elements are introduced, so that the problem of uneven dispersion of rare earth elements in a silicon dioxide matrix is avoided.

Drawings

FIG. 1 shows a block-shaped Y-SiO prepared in example 1 of the present invention₂Macroscopic view of aerogel.

FIG. 2 shows a block-shaped Y-SiO prepared in example 1 of the present invention₂N of aerogel₂Adsorption-desorption curves and pore size distribution plots.

FIG. 3 shows a block-shaped Y-SiO prepared in example 1 of the present invention₂SEM micrograph of aerogel.

Detailed Description

The invention is further illustrated by the following examples in conjunction with the accompanying drawings.

Example 1

The embodiment comprises the following steps:

(1) in a three-necked flask were charged 20.8g of TEOS, 55.2g of absolute ethanol and 5.4g H₂O, mechanically stirring for 15min, dropwise adding 0.05 wt% hydrochloric acid ethanol diluent into the mixture through a constant pressure funnel, stirring for 120min, sealing and standing at room temperature for 24h to obtain a molar ratio n (TEOS): n (C)₂H₅OH)︰n(H₂SiO (O) ═ 1: 12: 3₂And (3) sol.

(2) 34.8g Y (NO)₃)₃·4H₂Dissolving O powder in 10.8g water, heating at 50 deg.C for 30min, and cooling to room temperature to obtain Y (NO)₃)₃And (3) solution.

(3) 0.684g of the material obtained in step (2) is weighed and slowly dropped with 9.31g of SiO₂In the sol, magnetically stirring for 30 min.

(4) And (4) dripping ammonia water and ethanol diluent into the material obtained in the step (3), uniformly stirring, and standing for gelation.

(5) Will be provided withThe above Y-SiO₂Standing the gel for 24h in a sealed manner, performing supercritical drying, taking ethanol as a supercritical drying medium, and pre-charging N₂Until the pressure in the kettle is 2 MPa. The temperature in the kettle is raised to 270 ℃ at the heating rate of 1 ℃/min, and the temperature is kept for 2h until the pressure in the kettle is 10 MPa. Opening the water cooling device, slowly releasing the pressure in the kettle to normal pressure, and introducing N₂Blowing the mixture in a kettle, cooling the mixture to room temperature to obtain Y-SiO₂An aerogel.

(6) Bulk Y-SiO obtained in this example₂The macroscopic view of the aerogel is shown in FIG. 1, and the obtained aerogel has a density of 0.17g/cm³Having a specific surface area of 648.17m²In terms of/g, the mean pore diameter is 20.45 nm. N thereof₂The adsorption-desorption curve and pore size distribution are shown in fig. 2, and the aerogel microstructure is shown in fig. 3.

Example 2

The embodiment comprises the following steps:

(1) in a three-necked flask were charged 20.8g of TEOS, 32.2g of absolute ethanol and 5.4g H₂O, mechanically stirring for 15min, dropwise adding 0.05 wt% hydrochloric acid ethanol diluent 3.65g via constant pressure funnel at 6 s/drop speed, stirring for 120min, sealing and standing at room temperature for 24 hr to obtain molar ratio n (TEOS): n (C)₂H₅OH)︰n(H₂SiO (O) ═ 1: 7: 3₂And (3) sol.

(2) 34.8g Y (NO)₃)₃·4H₂Dissolving O powder in 10.8g water, heating at 50 deg.C for 30min, and cooling to room temperature to obtain Y (NO)₃)₃And (3) solution.

(3) 0.137g of the material obtained in the step (2) is weighed and slowly dropped with 12.8g of SiO₂In the sol, magnetically stirring for 30 min.

(4) And (4) dripping ammonia water and ethanol diluent into the material obtained in the step (3), uniformly stirring, and standing for gelation.

(5) Mixing the above Y-SiO₂Standing the gel for 24h in a sealed manner, performing supercritical drying, taking ethanol as a supercritical drying medium, and pre-charging N₂Until the pressure in the kettle is 2 MPa. The temperature in the kettle is raised to 270 ℃ at the heating rate of 1 ℃/min, and the temperature is kept for 2h until the pressure in the kettle is 8 MPa. The water-cooling device is turned on, and the water-cooling device is turned on,after the pressure in the kettle is slowly released to the normal pressure, N is introduced₂Blowing the mixture in a kettle, cooling the mixture to room temperature to obtain Y-SiO₂An aerogel.

(6) Bulk Y-SiO obtained in this example₂The density of the aerogel was 0.29g/cm³Having a specific surface area of 861.17m²In terms of/g, the mean pore diameter is 10.29 nm.

Example 3

The preparation method of this example includes the following steps:

(1) 20.8g TEOS, 92g absolute ethanol and 5.4g H were added to a three-necked flask₂O, mechanically stirring for 15min, dropwise adding 0.05 wt% hydrochloric acid ethanol diluent 3.65g via a constant pressure funnel at 6 s/drop speed, stirring for 120min, sealing and standing at room temperature for 24 hr to allow hydrolysis reaction to proceed sufficiently and slowly to obtain molar ratio n (TEOS): n (C)₂H₅OH)︰n(H₂SiO (O) ═ 1: 20: 3₂And (3) sol.

(2) 34.8g Y (NO)₃)₃·4H₂Dissolving O powder in 10.8g water, heating at 50 deg.C for 30min, and cooling to room temperature to obtain Y (NO)₃)₃And (3) solution.

(3) 0.228g of the material obtained in the step (2) was weighed and slowly dropped into 12.2g of SiO₂In the sol, magnetically stirring for 30 min.

(4) And (4) dripping ammonia water and ethanol diluent into the material obtained in the step (3), uniformly stirring, and standing for gelation.

(5) Mixing the above Y-SiO₂Standing the gel for 24h in a sealed manner, performing supercritical drying, taking ethanol as a supercritical drying medium, and pre-charging N₂Until the pressure in the kettle is 2 MPa. The temperature in the kettle is raised to 270 ℃ at the heating rate of 1 ℃/min, and the temperature is kept for 4h until the pressure in the kettle is 8 MPa. Opening the water cooling device, slowly releasing the pressure in the kettle to normal pressure, and introducing N₂Blowing the mixture in a kettle, cooling the mixture to room temperature to obtain Y-SiO₂An aerogel.

(6) Bulk Y-SiO obtained in this example₂The density of the aerogel is 0.10g/cm³Having a specific surface area of 844.28m²In terms of/g, the mean pore diameter is 13.22 nm.

Example 4

The embodiment comprises the following steps:

(1) 20.8g TEOS, 78.2g absolute ethanol and 5.4g H were added to a three-necked flask₂O, mechanically stirring for 12min, dropwise adding 0.1 wt% hydrochloric acid ethanol diluent 1.825g via a constant pressure funnel, stirring for 110min, sealing and standing at room temperature for 22h to obtain molar ratio n (TEOS): n (C)₂H₅OH)︰n(H₂SiO (O) ═ 1: 17: 3₂And (3) sol.

(2) 34.8g Y (NO)₃)₃·4H₂Dissolving O powder in 10.8g water, heating at 45 deg.C for 35min, and cooling to room temperature to obtain Y (NO)₃)₃And (3) solution.

(3) 0.684g of the material obtained in step (2) is weighed and slowly dropped with 11.8g of SiO₂In the sol, magnetically stirring for 30 min.

(4) And (4) dripping ammonia water and ethanol diluent into the material obtained in the step (3), uniformly stirring, and standing for gelation.

(5) Mixing the above Y-SiO₂Standing the gel for aging for 22h in a sealed manner, performing supercritical drying, taking ethanol as a supercritical drying medium, and pre-charging N₂Until the pressure in the kettle is 2 MPa. The temperature in the kettle is raised to 270 ℃ at the heating rate of 1 ℃/min, and the temperature is kept for 4h until the pressure in the kettle is 10 MPa. Opening the water cooling device, slowly releasing the pressure in the kettle to normal pressure, and introducing N₂Blowing the mixture in a kettle, cooling the mixture to room temperature to obtain Y-SiO₂An aerogel.

The method takes tetraethoxysilane and rare earth nitrate as raw materials, ethanol as a solvent, acid and alkali as catalysts, adopts a sol-gel method to prepare the rare earth doped silica wet gel, and obtains the massive rare earth doped silica aerogel after solvent replacement and ethanol supercritical drying. According to the method, the rare earth elements are doped into the silicon dioxide aerogel, so that the use temperature of the silicon dioxide aerogel can be increased, and the application of the aerogel under high-temperature extreme conditions is expanded. The density and microstructure of the aerogel can be controlled by controlling the ethanol content, the rare earth doping amount, the forming process and the like, so that the heat conductivity coefficient of the aerogel is controlled. The method has simple and easy process and high production efficiency, and is beneficial to large-scale production.

The above embodiments are only preferred embodiments of the present invention, but the implementation manner of the present invention is not limited by the above embodiments, and equivalent changes, modifications, substitutions and the like made according to the patent scope and the content of the specification of the present invention should still fall within the scope of the present invention.